High-temperature stability of Si/SiO2 interfaces and the influence of SiO flux on thermomigration of impurities in SiO2

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Abstract
We analyze experimentally unidirectional mass transport of As implanted into a SiO2 film covered with Si and heated to 1405 °C in a temperature gradient. The data can only be explained if we postulate that the thermomigration process is mediated by a flux of SiO molecules, flowing from the Si/SiO2 interfaces into the oxide. From the delay times before the onset of As drift, we estimate diffusivity of SiO at ∼4×10−13 cm2 /s at 1405 °C. The data also explain the apparent dichotomy between high-temperature dissociation of SiO2 , measured experimentally and predicted by thermodynamic arguments, and the ability to heat Si-coated SiO2 up to the melting point of Si at 1412 °C without any loss of the oxide integrity. The latter is possible because coated SiO2 saturates with SiO, resulting in steady-state conditions.